Rocket propulsion method



Nov. 27, 1956 F. J. MALINA 'ET AL ROCKET PROPULSION METHOD OriginalFiled May 8, 1943 IN V EN TOR. JOHN M PARSONS BY FRANK J. MAL/NAATTORNEY United States PatentO ROCKET PROPULSION METHOD Frank J. Malinaand John W. Parsons, Pasadena, Calif., assignors, by mesne assignments,to Aerojet-General Corporation, Cincinnati, Ohio, a corporation of OhioOriginal application May 8, 1943, Serial No. 486,236, now Patent No.2,573,471, dated October 30, 1951. Divided and application September 1,1950, Serial No. 182,742, now Patent No. 2,693,077. Again divided andthis application February 3, 1953, Serial No. 342,564

Claims. (Cl. 6035.4)

Our invention relates to jet propulsion and more particularly topropellants which are useful in connection therewith.

This is a division of my copending application Serial No. 182,742, filedSeptember 1, 1950, now Patent No. 2,693,077, as a division ofapplication Serial No. 486,236, filed May 8, 1943, now Patent No.2,573,471, issued October 30, 1951.

While our invention is capable of use in connection with the propulsionof a wide variety of different devices and vehicles, since it findsparticular utility in the propulsion of aircraft, its advantages aredescribed with relation to such use, it being understood that ourinvention is, however, not limited to such use.

Prior to our invention special means were always required to ignite thepropellants. For example, when liquid oxygen is used as an oxidizer andgasoline is used as a fuel, some auxiliary ignition means must always beprovided to initiate combustion of the propellants. This isobjectionable because it requires either a spark plug or other ignitoror means for heating the walls of the combustion chamber above theignition point of the propellant mixture making this system complex anddependent upon the operation of such ignition system.

While spontaneous combustion is obtained with our preferred combinationsof propellants which is especially effective when operating inaccordance with our preferred method it will be understood that thepropellants we have discovered offer advantages even when operatingunder other conditions.

The present invention relates to fuels, and oxidizers and theircombination as propellants and their method of injection into a jetmotor. Among the objects of our invention are: to provide more eificientand effective propellants for jet propulsion systems; to provide anoxidizing agent which is easily combustible with a suitable fuel andwhich has a large amount of oxygen available for burning a fuel; toprovide propellants, that is, fuels and oxidizers, which arespontaneously combustible; to provide a method for utilizing suchpropellants to give smooth combustion and to eliminate danger ofexplosion; to obviate the difficulties attendant upon the use ofliquified gases; to eliminate the need of an auxiliary ignition systemto ignite the propellants.

Oxidizers As a result of a thorough investigation of the variousoxidizing agents which may be used as propellants we prefer to employnitric acid. Since water tends to retard combustion of the acid with anyfuel, the nitric acid should be substantially free of water. Thus, Whitefuming nitric acid, which normally contains less than about 2% of waterby weight, is to be preferred to weaker solutions of nitric acid.However, we have found that more dilute solutions of nitric acid may beutilized provided that nitrogen dioxide is dissolved in the nitric acid;which is a way of increasing the concentration of an otherwise moredilute solution. Preferably the nitric acid should 2,771,739 PatentedNov. 27, 1956 contain at least about 5% N02 but preferably at leastabout 15 to 20% N02. Such a solution of nitrogen dioxide is known as redfuming nitric acid and almost all red fuming nitric acid which iscommercially available in this country contains between about 5% and 20%nitrogen dioxide by weight and less than about 5% water by weight.

Specifications for nitric acid, obtainable commercially as red fumingnitric acid, are as follows:

Chemical composition:

HNOs 90.5% by wt. min.

Water 2.5% by wt. max.

NOz 7.25% by wt. max-6.50% by wt. min. Physical properties:

Density 1.5 min.1.55 max. 70 F.

Melting point 50 F. max.

Color, etc. Orange to dark redfumes vigorously when exposed to air.

Specifications for nitric acid, obtainable commercially as white fumingnitric acid, are as follows:

Chemical composition:

Nitric acid 97.5% by wt. min.

Water 2.0% by wt. max.

N02 content 0.5% by wt. max.

Physical properties:

Density 1.46 min-1.52 max. 60 F.

Melting point F.

Color, etc. Straw yellow to water white; fumes vigorously when exposedto air.

The term white fuming nitric acid as used herein means a nitric acidcontaining a maximum of about 2% water by weight.

The term red fuming nitric acid as used herein means a nitric acidcontaining at least about 5% N02 and a maximum of about 5% water, byweight.

Nitric acid of all types containing at least 80% HNOs is useful as anoxidizer. We have also found that liquid nitrogen dioxide is a verysatisfactory oxidizer.

To eliminate the requirement for providing the jet motor with specialigniting means, we employ nitric acid,

' and preferably red fuming nitric acid, substantially free of water, asan oxidizer.

Fuels A. Aniline, orthotoluidine, and methylamine, B. Liquidhydrocarbons, containing large percentage-s of such amine substitutedorganic compounds.

Group II.Highly unsaturated hydrocarbons: Liquid hydrocarbons of theacetylene type and containing a large fraction of unsaturated (doubleand triple) carbon bonds, or both, for example, divinyl acetylene,dipropargyl, and propargyl alcohol.

Group III.Liquid substances containing the elements having theproperties of lithium (Li), beryllium (Be), boron (B), aluminum (Al),magnesium (Mg), phosphorous (P), potassium (k), and sodium (Na). Withthe exception of phosphorus all of the foregoing elements areparticularly useful in fuels because they generate large amounts of heatduring combustion, and phosphorus is particularly useful because it hasa low ignition temperature.

A. Liquid hydrides of those elements.

B. Liquid organo-metallic compounds containing one or more of suchelements.

C. Liquid fuels containing one or more such elements.

D. Liquid fuels containing one or more such elements in suspension.

All the above identified substances are spontaneously combustible withthe oxidizers hereinbefore discussed and are independently useful withother oxidizers where means for ignition is provided.

Of all these fuels we prefer to employ the amine substitutedhydrocarbons. Aniline, for example, not only has the advantage of beingspontaneously combustible with the oxidizers hereinbefore mentioned butis less hazardous than gasoline in the presence of air. While aniline istoxic it has the great advantage of being relatively inexpensive, eventhough more expensive than gasoline, and of being commercially availablein large quantities.

Method of operation The above mentioned oxidizers and fuels may be usedtogether as pairs of spontaneously combustible propellants atatmospheric temperature and pressure. However, if desired theseoxidizers and fuels may be used with other fuels (such as gasoline) orother oxidizers (such as liquid oxygen) respectively.

So far as We know we are the first to achieve sponprefer to use thefuels and oxidizers hereinbefore mentioned.

Certain difficulties are encountered when utilizing these propellantsfor propulsion. Unless the propellants are supplied to the jet motorunder the proper conditions the motor is liable to fail completely, topulsate in its operation, or to explode, even though the propellants aresupplied at uniform rates.

These difiiculties may be eliminated and certainty and smoothness ofoperation secured by so relating the rates of injection of fuel andoxidizer to the size of the jet chamber and the inherent ignitionproperties of the mixture that explosion of the combustible mixture isavoided during the initial combustion, and subsequent injection occursat rates conducive to the combustion of the continuously suppliedpropellants so as to avoid the accumulation in the jet chamber of anysubstantial amount of the unburned propellants. To achieve this result,we initially inject propellants into the combustion chamber at ratessuch that the amount of propellants injected prior to the initiation ofcombustion is less than about 20% of the volume of the combustionchamber.

After combustion has been initiated, the propellants may be injected ata greater rate than they are injected initially inasmuch as the timeinterval between their injection and combustion is reduced because ofthe higher temperature and pressure of the mixture resulting from priorcombustion and the heating of the walls of the combustion chamber by theproducts of combustion.

In the drawing the figure shows a jet motor system including tanks andconduits for supplying propellants to the motor.

The fuels and oxidizers hereinbefore described are advantageouslyemployed in the propulsion of an aircraft by providing the fuel andoxidizer separate containers 11 and 12 respectively connected in anysuitable manner as by pipes 13 and 14 to a jet or combustion chamber.Throttle valves 16 and 17 energized by electrical circuits 18 and 19 areprovided in said pipes to control the rates of supply of the fuel andoxidizer respectively to the combustion chamber 15. A receptacle 20 isconnected by a conduit 21 having a pressure regulator 22 therein to thereceptacles 11 and 12 and is provided with a gas under pressure,preferably a gas inert with respect to either propellant. Preferably thecontainer for the fuel and the container for the oxidizer are connectedto a source of pressure adapted to force the contents of such containersinto the jet or combustion chamber at controlled rates determined by thedegree of opening of the valves in said pipes.

The practice of the method of our invention contemplates so relating therates of injection of the oxidizer and of the fuel to the combustion orjet chamber to their inherent combustion properties and the size andtemperature of the chamber that smooth non-explosive combustion occursinitially and throughout the entire operation While providing thedesired quantity of propulsive power. Our invention is particularlyadvantageous when the combustion chamber is initially at atmospherictemperature, or at the temperature of any other medium in which themotor is to operate, as we are able to achieve combustion initiallywithout auxiliary ignition or preheating of the chamber or thepropellants.

If the propellants are supplied at such initial rates, then, when thepropellants are initially injected into the jet motor, the initiallyburned propellants soon fill the combustion chamber with hightemperature gases and vapors which heat the incoming propellants therebyvaporizing them and reducing the ignition time lag. Then thesubsequently injected propellants burn spontaneously Without anysubstantial accumulation of propellants in the liquid phase.

As an example, applied to a combustion chamber having a length of about10 inches and a cross sectional area of about 7 square inches, highlyconcentrated nitric acid and aniline operate very satisfactorily whenthey are injected into the combustion chamber initially and prior tocombustion at the rates of 3.6 lbs. per second and 2.4 lbs. per secondrespectively.

While these propellants and method of use and the apparatus for theiruse in propelling aircraft or other devices, which are hereinbef-oredescribed, are fully capable of providing the advantages primarilystated, it will be recognized by those skilled in the art that variousmodifications and alterations may be made therein while still providinguch advantages, and our invention is there fore to be understood as notlimited to the specific embodiments hereinbefore described but asincluding all modifications and variations thereof coming within thescope of the claims which follow.

We claim as our invention:

1. The method of producing thrust which comprises ejecting from areact-ion chamber the gaseous products produced by the spontaneouscombustion of an acid, selected from the group consisting of red fumingnitric acid and white fuming nitric acid, and a liquid fuel consistingessentially of an element selected from the group consisting of lithium,beryllium, boron, aluminum, magnesium, phosphorous, potassium, sodiumand mixtures thereof, dispersed in liquid hydrocarbon.

2. The method of producing thrust which comprises ar n ejecting from 'areaction chamber the gaseous products produced by the spontaneouscombustion of an acid, selected from the group consisting of red fumingnitric acid and white fuming nitric acid, and a liquid fuel consistingessentially of an element selected from the group consisting of lithium,beryllium, boron, aluminum, magnesium, phosphorous, potassium, sodiumand mixtures thereof, dispersed in gasoline.

3. The method of producing thrust which comprises ejecting from areaction chamber the gaseous products produced by the spontaneouscombustion of red fuming nitric acid and a liquid fuel consistingessentially of a suspension of lithium in gasoline.

4. The method of producing thrust which comprises ejecting from areaction chamber the gaseous products produced by the spontaneouscombustion of red fuming nitric acid and a liquid fuel consistingessentially of a suspension of sodium in gasoline.

5. The method of producing thrust which comprises ejecting from areaction chamber the gaseous products produced by the spontaneouscombustion of red fuming nitric acid and a liquid fuel consistingessentially of a suspension of potassium in gasoline.

6. The method of producing thrust which comprises ejecting from areaction chamber the gaseous products produced by the spontaneouscombustion of red fuming nitric acid and a liquid fuel consistingessentially of a suspension of phosphorous in gasoline.

7. The method of producing thrust which comprises ejecting from areaction chamber the gaseous products produced by the spontaneouscombustion of white fuming nitric acid and a liquid fuel consistingessentially of a suspension of lithium in gasoline.

8. The method of producing thrust which comprises ejecting from areaction chamber the gaseous products produced by the spontaneouscombustion of White fuming nitric acid and a liquid fuel consistingessentially of a suspension of sodium in gasoline.

9. The method of producing thrust which comprises ejecting from areaction chamber the gaseous products produced by the spontaneouscombustion of White fuming nitric acid and a liquid fuel consistingessentially of a suspension of potassium in gasoline.

10. The method of producing thrust which comprises ejecting from areaction chamber the gaseous products produced by the spontaneouscombustion of White fuming nitric acid and a liquid fuel consistingessentially of a suspension of phosphorous in gasoline.

References Cited in the file of this patent UNITED STATES PATENTS515,500 Nobel Feb. 17, 1894 1,506,323 ONeill Aug. 26, 1924 1,532,930ONe'ill Apr. 7, 1925 2,013,152 Hoyt Sept. 3, 1935 2,055,210 Vose Sept.22, 1936 FOREIGN PATENTS 195,064- Great Britain Apr. 24, 1924 476,227Great Britain Dec. 3, 1937

1. THE METHOD OF PRODUCING THRUST WHICH COMPRISES EJECTING FROM AREACTION CHAMBER THE GASEOUS PRODUCTS PRODUCED BY THE SPONTANEOUSCOMBUSTION OF AN ACID, SELECTED FROM THE GROUP CONSISTING OF RED FUMINGNITRIC ACID AND WHITE FUMING NITRIC ACID, AND A LIQUID FUEL CONSISTINGESSENTIALLY OF AN ELEMENT SELECTED FROM THE GROUP CONSISTING OF LITHIUM,BERYLLIUM, BORON, ALUMINUM, MAGNESIUM, PHOSPHOROUS, POTASSIUM, SODIUMAND MIXTURES THEREOF, DISPERSED IN LIQUID HYDROCARBON.